Thermal relay



C. F. GRINE THERMAL RELAY July 29, 1952 Filed March 17, 1950 l O a 23 Fig.2. 25 A [gym lnsglotion 2 Insulation v lnsulotio'n INVENTOR Charles F. Grine.

WITNESSES: (My/m ATTORNEY C. F. GRINE' THERMAL RELAY July 29, 1952 Filed March 17, 1950 Fig.4.

8 e e n l l R Y m m m E N N h 0 k M E F N w 0 4M 0 V S T L L me -T n H II A 0 0 r N N Ga TL f Y f f g @M .w b 6 FY mg m 0 11? f L ms m O 7. 2 g F 2 2 6 C 81 Patented July 29, 1952 VUNITED STATES ea'reur OFFICE THERMAL RELAY Charles F. Grinc, Saegertown, Pa., assignor to WestinghouseElectric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 17, 1950, Serial No. 150,290

8 Claims.

My invention relates to thermal relays, and more particularly to a temperaturefcompensated adjustable relay of the type disclosed in the pat ent to Paul R. Lee, entitled Current Limiting Relay, No. 2,280,960.

Nearly every household using electricity has a number of load units some of which, when in use, are not to be disconnected from the supply lines, as, for example, the electric range or the ironer, or certain lights etc., and others as the water-heater, certain fans, or certain lights, etc. may without substantial inconvenience to the user be disconnected from the supply lines.

Load units of the first class are, amongst engineers dealing with household load units, often known'as non-'deferrable loads, whereas the load units of the second class are, amongst the same group of engineers, known as deferrable loads.

If means are provided in each household for delaying the'use of deferrable loads until the non-deferrable loads are no longer connected to the supply Io'ada'localiz'ed load-peaks on the dis tribution system are eliminated at the very source. The chances of distribution failures from lc'alized'load-peaks are thus eliminated.

The above-mentioned patent, No. 2,280,960, is

directed toward 'a solution of the problem menticned, "but since all households, particularly if an ironer 'or an electric range is used, have a three-wire system supplying llo volt and 220- volt'circuits, the current limiter of the prior art does not provide proper'protection, nor does the rela sense unbalance conditions in the circuits.

One "object of my invention is the provision of a thermal relay in a three-wire system that is responsive both to certain unbalance'conditions and certain load currents for eiiecting the disconnection of the deferrable load from the threewiresystem.

A broader object of my invention is the provision, in'a load circuit, of a thermal relay responsive to a certain efiective load current traversing the relay for efiectingthe deenergization of a certain unit or 'unitsof the load circuit.

A further object of my invention is the provision of a thermal relay, for controlling the energization of certain units of a load circuit, having means associated therewith for compensating for changes in ambient temperature.

Theobjects stated are merely illustrative.

Still other objects of my invention will be come apparent from a study of the following specification and accompanying drawings, giving a more detailed disclosure of my contribution to the art. In the drawings:

. crease in temperature.

Figure 1 is a plan View of a thermal relay embodying my invention;

Fig. 2 is a side view of the showing in Fig. 1;

Fig. 3 is a view on section line III-III of Fig. 2;

Fig. 4 is a view on section line IV-IV of Fig. 2;

Figs. 5 and 6 are side views, with certain parts broken away, illustrating two operative positions, respectively; and

Fig. 7 shows a wiring diagram and shows the thermal elements and contacts of the relay of the features of my invention.

Referring to the accompanying drawings in which like reference characters indicate like parts in the several views, I show a thermal relay I comprising a supporting structure having the top and bottom plate members 2 and 3 suitably rigidly connected to each other by bolts or rivets 4, provided with the spacing sleeves 5.

Terminal straps 6 and 1 are at the right rigidly secured to theeplates 2 and 3, respectively, through suitable shims of insulation shown.

Intermediate the ends of plate 2, but nearer the left end thereof I rigidly secure the vertical- .ly disposed stud 8. to plate 2. To the bottom .lation with the spring.

The free end of the strap is provided by means of a rigid connection withfa shim of insulation ll carrying an electric contact 12. By means of a pigtail connection 13, the electric contact I2 is connected to the terminalstra'pt.

The bimetallic strap I0 is responsive to ambient temperature and one rise of temperature swings clockwise with respect to its connection and in a counterclockwise direction upon a de- To make the temperature compensation adjustable, I provide the plate 2 with the graduated and calibrated spring ad justing means l4.

The U-shape'd bimetallic member I5 is, at the endsof the legs of the U, rigidly secured to the plate 3, through the contact straps I6 and IT.

A suitable spacer [8 of insulation insulates the plate 3 from the straps 16 and I1. To the bight of the U-shaped member IS, the stiff shim iii of insulation is rigidly secured. The shim l9 carries the electric contact 20. By means of the pigtail connection 2|, the contact 20 is electrically connected to the contact strap I. The disposition of the contacts l2- and 20 is such that they are normally in contact and the member I 5 is so disposed thatrt swings clockwise upon a rise in temperature and counterclockwise upon a decrease in temperature.

A second U-shaped bimetallic member 22 is, at the ends of the legs of the U, rigidly secured to the plate 2 through the terminal, or contact, straps 23 and 24. A suitable spacer 25 of insulation insulates the terminal straps 23 and 24 from the plate 2.

To the bight of the U-shaped member 22, the plunger 26 of insulation is rigidly secured and the normal disposition of the plunger 26 is such that it engages the shim l9 at the bight of the U-shaped member l5 with a slight pressure. Further, the member 22 is. so mounted that a rise in temperature of the member 22 will cause the plunger to move clockwise with reference to its point of connection and move counterclockwise upon a decrease in temperature.

From the foregoing, it is apparent that all the bimetallic elements move in unison with changes in ambient temperature and in consequence the same amount of extra heating of the elements, or members l5 and 22, regardless of the ambient temperature, is necessary to cause interruption between contacts 12 and 20. There is thus effective ambient temperature compensation and such compensation may be adjusted by the means [4.

Good electrical contact between the faces of contacts [2 and 20 is assured by the wiping action provided between the contact faces. As viewed in Fig. 2, for example, the contact faces lie between the actuating bimetals I and i at the free extremities of which the contacts l2 and 20 are respectively supported. This arrangement therefore provides contact mountings for contact movement substantially along an arcuate path, in each case defined essentially by the radius between the respective contacts and the corresponding fulcrum of the contact supporting structure and intersecting at the point of contact of one contact face with the other. Since the radii of the contact paths are differ-l ent, that for the contact l2 being the shorteni and the centers of the arcuate paths are displaced both laterally and radially, movement of the contacts in the same general direction, for example, down as seen in Fig. 2, results in displacement of the contact faces in opposite directions respectively, substantially at right angles to the downward path of motion. As a consequence, the contact faces are wiped, one across the other upon contact motion as described. Similarly, if the contacts are separated and contact 20 moves upwardly to engage contact l2, a wiping action again occurs until the contact motion ceases.

As shown in Fig. 8, in practice the bimetallic member I 5 is connected in series with the circuit of the load units between conductors A and B comprising non-deferrable load units, and the bimetallic member 22 is connected in series with the circuit of the load units between conductors B and C, comprising further non-deferrable load units. The electric range, certain lights, ironer, etc. usually constitute non-deferrable loads.

A typical deferrable load is the electric water heater. The deferrable load is connected in series with contacts I2 and 20 and across conductors A and C.

If the load in the circuit A and B is perfectly balanced by the load in circuit B to C; the bimetallic members [5 and 22 move clockwise together to interrupt the circuit for the deferrable load at contacts l2 and 20.

If the circuit loads are not balanced, then the thermal relay will still disconnect the deferrable load when the demand is greater than a given value. For example, when the demand is greater in the circuit including bimetallic member l5 than in the circuit including the bimetallic member 22, then the operation will be as shown in Fig. 5. When the demand in the circuit including the bimetallic member 22 is greater, then the bimetallic member 22 will carry the member [5 along with it and the operation will thus be as indicated in Fig. 6.

My invention thus provides a single relay for current demand limitation regardless of which circuit of a three-wire system carries the greater load.

While the forms of the embodiments of my invention as herein disclosed constitutes the preferred forms, it is to be understood that other forms may be devised all falling within the scope of my invention.

I claim as my invention:

1. In a current limiting device for an electric load circuit of the three-wire type, having load units across each pair of wires which disconnects the load units across one pair of wires when the load demand across either of the two other pairs of wires is above a selected value, the combination of, a supporting structure, a first bimetallic member fixed at one end to the said structure and carrying at its other end an electric contact insulated from the bimetallic member, said first bimetallic member being responsive to the ambient temperature to cause movement of the contact in a given direction on a rise in ambient temperature, a second bimetallic member rigidly fixed at one end to the said structure and carrying at its other end on electric contact insulated from the second bimetallic member and normally engaging the electric contact on the first bimetallic member, said second bimetallic member being connected to carry the load current of the load units connected across one pair of wires and being disposed to deflect in the same direction upon a rise in temperature as the deflection of the first bimetallic member, said electric contacts at the free ends of the first and second bimetallic members being in series with the load units connected across a second pair of wires, a third bimetallic member rigidly connected at one end to said structure and carrying at its free end a contact of insulating material normally engaging the second bimetallic member near the free end, said third bimetallic member being connected to carry the load current of the load units connected across a third pair of wires and being so disposed with respect to the second bimetallic member that the contact of insulating material will upon a rise in temperature of the third bimetallic member move in the same direction as the first two bimetallic members and upon independent movement of the third bimetallic member cause interruption of the normally engaging electric contacts on the free ends of the first and second bimetallic members.

2. In a current limiting device for an electric load circuit of the three-wire type, having load units across each pair of wires which disconnects the load units across one pair of wires when the load demand across either of the two other pairs of wires is above a selected value, the combination of, a supporting structure, a first bimetallic memher fixed at one end to thesaid structureandcarwing at its other end an electric contact insulated from the bimetallic member, said firstbimetallic member being responsive to the ambient temperature to .cause movement of the contactin a given direction on-a rise in ambient temperature, a second bimetallic member rigidly'fixed at one endto the said structureandcarrying atits other end an electric contact insulated from the second bimetallic member and normallyengaging theelectric contact on the first bimetallic member to establish a circuit for a certain load unit, said second bimetallic member being connected to carry the load current of the load units connected across one pair of wires and being disposed to deflect in the same direction as the deflection of'thefirst bimetallic member upon 'a rise in temperature of the second bimetallic mem ber, and a third bimetallic member rigidly connected at one end to said structure and carrying at its free end a contact of insulating material normallyengaging thesecond bimetallic member near the free end, said third bimetallic member being connected to carry'the load current of the load units connected across a second pair of wires and being so disposed with respect to the second bimetallic member that the contact of insulating material will upon a rise in temperature of the third bimetallic member move in the same direction as the first two metallic members and upon independent movement of the third bimetallic member cause interruption of the normally engaging electric contacts on the free ends of the first and second bimetallic members to open the circuit of saidcert'ain load units.

3. Ina current limiting relay for a three-wire circuit system of load units, in combination, a supporting structure comprising a pair of vertically spaced horizontally disposed plates rigidly secured to each other, a fiat spring at one end rigidly secured to one of said plates, an ambient temperature responsive bimetallic strap at one end secured to the free end of the spring, strap having an. electric contact, insulated from the strap, secured to the free end of the strap, a flat bimetallic member at one end rigidly secured to one of said plates, said member having an electric contact, insulated from the member, secured to the free end of the member, said contacton the strap and said contact on the member being normally'in engagement with each other, a second fiat bimetallic member also at one end secured to one of said plates and having its free end disposed. between said bimetallic strap and first bimetallic member, a contact of insulation secured to the free end of the second bimetallic member, said. contact of insulation normally engaging the flat bimetallic member, said bimetallic members and strap being so disposed with respect to each other that like changes of temperature cause like movements of the free ends of the members and strap. one of the bimetallic members being associated with the load units in one circuit to be responsive in its movement of its free end to the current demand in that circuit. the other bimetallic member being associated with the load units in the other circuit to be responsive in its movement of its free end to the current in the second circuit. and circuit means for connecting the load units of the third circuit in series with the contacts on the free end of the bimetallic strap and the free end of the first bimetallic member.

4. In a current limiting relay for a three-wire circuit system of load units, in combination, a supporting structure comprising a pair of verti- 6 cally spaced horizontally disposed plates rigidly secured to'eachpther, a fiatspringat :one end rigidly secured to one i of said plates, an ambient temperature responsive bimetallic strap at one endsecured to the free end of the spring, an adjusting screw threaded in the top plate and disposed .to shift thefree end of the spring vertically to thus vertically adjust the point of connection of the bimetallic strap to thus adjust the strap fordifierentambient temperatures, said strap having'an electric contact, lnsulated from the strap secured to the free end of the strap, a flat bimetallic member at one end rigidly se cured to one I of said plates, said member having an-electric contact, insulated from the member, secured tothe freeend of the member, said :contact onthe strapand said contact on the member being normally in engagement with each other, a-second fiat bimetallic member also at one end secured to oneof said plates and having its free end disposed between said bimetallic strap andfirst bimetallic member, a contact of insulation secured to the free end ofthe second bimetallic member, said contact of insulation normally engaging the first bimetallic member, said bimetallic members and strap being so disposed with respect to each other that like'changes of temperature cause like movements of the free ends of the-members and strap, one of the bi.- metallicmembers being associated with the load units in one circuit to be responsive in its movement of its free end tothe current demand in that circuit, the other bimetallic member being associated with the load units in the other circuit to be-responsi-ve in its movement of its free end to the current in the second circuit, and circuit means for-connecting theload 'units of the third circuit in series with the contacts'on the free end of the bimetallic strap and-the free end of the first bimetallic member.

5. Ina current limiting relay for athree-wire circuit system ofload units, in combination, a supporting structure comprising a pair of vertically spaced horizontally disposed plates rigidly secured to each other,1a flat spring at one end rigidly secured'to one of said plates, an ambient temperature responsive bimetallic strap at one end secured to the free end of the spring,'an adjusting screw threaded in the top plate and disposed to shift the free end of the spring vertically to thus vertically adjust the point of connection of the bimetallic strap to thus adjust the strap for different ambient temperatures, said strap having an electric contact, insulated from the strap, secured to the free end of the strap, means mounted on the strap for vertically adj usting the armature, a flat bimetallic member at one end rigidly secured to one of said plates, said member having an electric contact, insulated from the member, secured to the free end of the member, said contact on the strap and said contact on the member being normally in engagement with each other, a second fiat bimetallic member also at one end secured to one of said plates and having its free end disposed between said bimetallic strap and first bimetallic member. a contact of insulation secured to the free end of the second bimetallic member, said contact of insulation normally engaging the first bimetallic member, said bimetallic members and strap being so disposed with respect to each other that like changes of temperature cause like movements of the free ends of the members and strap, one of the bimetallic members being associated with the load units in one circuit to be responsive in its movement of its free end to the current demand in that circuit,-the other bimetallic member being associated with the load units inthe other circuit to be responsive in its movement of its free end to the current in the second circuit, and circuit means for connecting the load units of the third circuit in series with the contacts on the free end of the-bimetallic strap and the free end of the first bimetallicmember'.

6; A current limiting relay Tor a three-wire household electric power-circuit including a load unit between the first and second'wire, a load unit between the second and third wire, and a load unit between the first and third wire, in combination, a supportin structure comprising a pair of vertically spaced horizontally disposed plates, a flat spring at one end rigidly secured to one of said plates and disposed in a vertically spaced relation to said plates, and adjusting screw for vertically adjusting the free end of the spring, a temperature responsive strap at one end rigidly secured to the free end of the spring, said strap being in substantial alignment-with said spring, an electric contact insulated from the strap, secured to the free end of the strap, a flat bimetallic member at one end secured to said plates, said member having an electric contact, insulated from the member, secured to the free end of the member, said contact on the strap and said contact on the member being normally in engagement with each other, said member and strap being so disposed with respect to each other that like temperature changes cause likemovements of free ends of the member and strap, circuit means for heating the member as afunction of the load current of one load unit to effect movement of the member, at its free end, away from the free end of the strap, whereby the contacts are caused to be disengaged from each other, and circuit means normally connecting one of the load units, other than the one whose load current affects the operation of said member, in series with" saidelectric contacts.

7. In a current limiting control for a three- 8 tallic member, secured to the free end of the first bimetallic member, said first bimetallic member being connected in series with the load units across one pair of wires, a second bimetallic member at one end secured to the structure and at the free end mechanically engaging the first bimetallic member, said second bimetallic memher being connected in series with the load units across a second pair of wires, the disposition of the bimetallic members and ambient temperature responsive member is such that a like change in temperature of all of them causes them to deflect the same amount in the same sense to thus maintain the electric contacts in engagement, whereas an unlike change of the temperature of the members causes a disengagement of the electric contacts to thus interrupt the circuit of the load units connected across the third pair of wires.

8. In a current limiting control, in combination, an electric load circuit including a thermostatic device producing a mechanical movement proportional to the load current in the load circuit, a second load circuit also including a thermostatic device producing a mechanical movement proportional to the load current in the second load circuit, a third electric load circuit including in series therewith a pair of electric contacts, means associated with the first thermostatic device for moving one of the electric contacts away from the other upon a predetermined rise in the load current in the first load circuit, means associated with the second thermostatic device for actuating the first thermostatic device to cause the movement of one of the electric contacts away from the other upon a predetermined rise in the load current in the second load circuit, whereby the third load circuit is interrupted When the load current in either of the first two load circuits rises above a selected value.

CHARLES F. GRINE,

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Kercher Sept. 5, 1950 

